The field of this disclosure relates generally to a rotor blade and method of fabricating the same and, more particularly, to cooling a rotor blade.
At least some known rotor blades include tip shrouds to prevent leakage of gases past the tips of the rotor blades and to facilitate increasing operating efficiency. However, known tip shrouds may experience creep due to temperatures and loading during operation. By reducing the temperature of the shrouds during operation, the service life of the shroud may be extended. However, known tip shroud cooling features add weight to the extremities of the shroud and may increase the bending stresses in the shroud fillet and the blade airfoil. Further, although known tip shrouds generally increase aerodynamic efficiency, known tip shrouds may be limited by a mechanical gap that sets the leakage across seal teeth.
One known shroud cooling feature includes circumferential cavities cast within the rotor blade to cool the tip shroud. More specifically, the cavities are cast within the tip shroud using ceramic cores. However, such rotor blade fabrication results in a heavier blade due to casting constraints and in lower casting yields due to wall thickness variations and/or core breakage. Another known shroud cooling feature includes cooling holes drilled through the tip shroud. More specifically, the tip shroud cooling holes intersect holes drilled through the airfoil to provide the cooling air. However, such cooling holes require deep hole drilling technology and precise alignment and/or placement to ensure that the holes intersect. Moreover, high stress concentrations may exist at the intersection of the cooling holes regardless of alignment and over drills.